DISPERSION CHARACTERISTICS OF CERAMIC POWDERS IN THE APPLICATION OF CATIONIC AND ANIONIC POLYELECTROLYTES

Dispersion characteristics of silicon nitride, silicon carbide, alumin a, aluminum nitride and yttria powders in aqueous solutions of anionic and cationic polyelectrolytes were studied by measuring particle size distribution using a gravity sedimentation technique. The influence o f polyelectrolyte concentration and suspension pH on the dispersion wa s examined. All powders examined in this study could be well dispersed in the presence of either cationic or anionic polyelectrolyte by adju sting the dispersion pH to at least 2.5 pH units away from the effecti ve pH(iep) (iep=isoelectric point) of the powder-polyelectrolyte syste m. The dispersion characteristics of these powders in the presence of polyelectrolytes are explained in terms of interfacial interactions in the powder-polyelectrolyte systems. These interactions between the po wder and polyelectrolytes as a function of suspension pH, and possible mechanisms leading to the stability of particles in a dispersion, are discussed.